Endoluminal grafts are intraluminal conduits that are generally comprised of a scaffolding (usually a metal stent) that is covered or lined with a fabric or graft material. As such, these are often termed “stent grafts.” These conduits direct blood flow from one portion of the vasculature to another. The fabric portion provides containment of blood pressure within the conduit, thereby excluding the pressure from the vascular pathology (i.e., aneurysm or dissection A, see FIG. 1A) in which they are placed. Suitable materials and methods for fabricating such grafts, delivering them to their desired position in the body, and deploying them are well known in the art.
To be effective, endoluminal grafts must be deployed in a position where their proximal and distal ends provide an occlusive seal in a healthy portion of the blood vessel proximal and distal to the pathology being treated (FIG. 1B). These seal zones are critical for exclusion of the systemic blood pressure from the treated (diseased) segment such as aneurysm or dissection A.
In many instances, there are important branch vessels that originate in either the diseased segment or the seal zone (FIG. 2A) that would need to be sacrificed if the pathology were to be treated using a single standard endoluminal graft such as is shown in FIG. 1A. In contrast, the use of multiple endografts placed side by side in the seal zone can feasibly preserve flow in these important branch vessels while still excluding pressure from the diseased segment (FIG. 2B). This strategy has become an increasingly popular method for endovascular repair of aneurysms involving challenging anatomy such as branch vessels. In the art, it is commonly referred to as the “snorkel” or “chimney” technique. In most cases there is a larger main endograft used to treat the vascular pathology (usually in the aorta) and one or more smaller-diameter endografts (snorkels) placed alongside of it to preserve flow into the branch vessels (e.g., renal, mesenteric, or carotid arteries). In this manner, blood flow is preserved in these branch vessels that would otherwise have to be covered or excluded by the main endograft to achieve a good seal for exclusion of the diseased blood vessel segment.
However, one of the weaknesses of this technique is the imperfect nature of the seal inherent to the multiple side-by-side grafts. Conventional endografts typically define a circular cross-sectional dimension. Because each of the main endograft and snorkels define such a circular cross-sectional dimension, the snorkels interfere with the required occluding seal (see FIG. 1B for an illustration of a proper seal) of an end of the main endograft provided with such snorkels. The branch vessel grafts (snorkels) interfere with apposition of the main endograft to the blood vessel wall in the seal zone, leading to gutters alongside the snorkel that could allow continued pressurization of the diseased segment. This is best seen in FIG. 2B. Indeed, even attempts to overinflate or oversize a conventional circular/cylindrical endograft to force it to wrap around the smaller snorkel endografts have shown that undesirable gutters remain.
There is accordingly identified a need in the art for an endoluminal graft for use in parallel endograft techniques which, while effective for its intended purpose, provides additional advantages in preventing “gutters” alongside the ancillary or snorkel endografts, providing a good occlusive seal of the main endograft with a blood vessel wall and preventing blood leakage and potentially continued pressurization of the blood vessel lesion.